In the evolution to all Internet Protocol (IP), a communication network needs to ensure end-to-end Quality of Service (QoS) to provide services that satisfy users. An IP network provides various services (such as multimedia call, file downloading, and web browse). Different services require different QoS (including bandwidth, delay, and packet loss ratio), and employ different charging rules (such as online charging, offline charging, flow-based charging, or time-based charging).
To meet the QoS and charging requirements, the 3rd Generation Partnership Project (3GPP) defines a PCC architecture, which fulfills different QoS control and charging requirements.
As shown in FIG. 1, the 3GPP TS 23.402 defines two roaming scenarios in the PCC architecture: Home Routed and Local Breakout. Home Routed means that: A Packet Data Network Gateway (P-GW) is located in a Home PLMN (HPLMN), and the data needs to be connected to the Application Server (AS) through the home gateway. Local Breakout means that the P-GW is located in a Visited PLMN (VPLMN), and the data is connected to the AS not through the home gateway, but through the visited gateway.
In a Home Routed roaming scenario (as shown in FIG. 1a), a gateway control session (namely, a Gxx session) is created between a Serving Gateway (S-GW) and a Visited Policy Control and Charging Rules Function (V-PCRF or VPCRF). The V-PCRF forwards information to a Home Policy and Charging Rules Function (H-PCRF or HPCRF) through an S9 interface, and transmits the policy generated by the H-PCRF to the S-GW. An IP Connectivity Access Network (IP-CAN) session (namely, a Gx session) is created between the P-GW and the H-PCRF. The gateway control session information and the IP-CAN session information are transmitted to the H-PCRF respectively, and the H-PCRF generates policies. In this scenario, the IP-CAN session information of the P-GW does not pass through the V-PCRF.
In a Local Breakout roaming scenario (as shown in FIG. 1b), a gateway control session is created between the S-GW and the V-PCRF, and an IP-CAN session is created between the P-GW and the V-PCRF. The V-PCRF processes the gateway control session information and the IP-CAN session information, and then forwards the information to the H-PCRF. The H-PCRF generates policies. The H-PCRF delivers generated PCC rules to the V-PCRF. The V-PCRF extracts information from the PCC rules to generate QoS rules, sends the PCC rules to the P-GW and sends the QoS rules to the S-GW. In this scenario, the V-PCRF decides whether to transmit the gateway control session information to the H-PCRF according to information such as the PDN identifier (ID) and roaming agreement. The IP-CAN session information of the P-GW is sent to the V-PCRF. The V-PCRF processes the information and generates an S9 session, and transmits the information to the H-PCRF.
For ease of understanding, the terms involved in the PCC architecture are described below:
IP-CAN: If the IP service connectivity is maintained (namely, without interrupting the service) when a user roams in an access network (changes the location), such an access network is called “IP-CAN”. Examples of an IP-CAN include a General Packet Radio Service (GPRS) network and an Interworking Wireless Local Area Network (I-WLAN).
IP-CAN session: An IP-CAN session refers to a connection relation between a user and a PDN ID (for example, the ID indicates that the network is the Internet), and this connection relation is identified by the IP address of the user and the user ID (for example, an International Mobile Station Identity (IMSI) in the 3GPP). The IP-CAN exists only if the user is allocated an IP address and can be identified by the IP network. The IP-CAN session may include one or more IP-CAN bearers.
S9 session: The S9 session is a session between the V-PCRF and the H-PCRF, designed to transmit IP-CAN session information, gateway control session information or Rx information to the H-PCRF, and also designed for the H-PCRF to transmit PCC (including QoS) rule information.
Besides, the functional entities in the PCC architecture are described below:
S-GW: The S-GW is responsible for processing the mobility of the user, and interacts with the P-GW through an S5/S8 interface over the GPRS Tunneling Protocol (GTP) or Proxy Mobile Internet Protocol (PMIP), and interacts with the PCRF through a gateway control session interface (namely, a Gxx interface) by means of Diameter messages.
P-GW: The P-GW is responsible for communications with the external PDN (Internet, or IP service defined by an operator such as IP Multimedia Subsystem (IMS)) through an SGi interface (not illustrated in the figure), and interacts with the S-GW through an S5/S8 interface over GTP or PMIP, and interacts with the PCRF through an IP-CAN interface (Gx interface) by means of Diameter messages.
H-PCRF: The H-PCRF is responsible for policy decision and flow-based charging control. The H-PCRF decides the corresponding policy according to the policy of the operator, user subscription data (obtained from a Subscription Profile Repository (SPR)) and the ongoing service information (obtained from an Application Function (AF)), and provides the policy to a Policy and Charging Enforcement Function (PCEF), and the PCEF enforces the policy. The policy may be PCC rules or independent properties. For ease of description, the description herein ignores the nuances between the policy and the PCC rule. The H-PCRF provides the QoS policy to a Bearer Binding and Event Reporting Function (BBERF). The BBERF performs the QoS and the session control function. The policies include rules for detecting service data flows (namely, a set of IP flows for implementing a service such as voice communications), gating or not, QoS, and flow-based charging rule.
V-PCRF: The V-PCRF exists in a Local Breakout scenario, and sends the service information provided by the visited AF and the IP-CAN session information of the P-GW to the H-PCRF, and provides an event reporting function. The V-PCRF provides operator policies in the visited network so that the H-PCRF can formulate PCC rules. The V-PCRF transmits the PCC policies formulated by the H-PCRF to the P-GW, transmits the QoS policy formulated by the H-PCRF to the S-GW, and answers the gateway control session. In a Home Routed scenario, the V-PCRF reports events to the H-PCRF, and provides the operator policies in the visited network so that the H-PCRF can formulate PCC rules; the V-PCRF transmits the QoS policy formulated by the H-PCRF to the S-GW, and answers the gateway control session.
PCEF (included in the P-GW): The PCEF detects service data flows, enforces policies, and performs flow-based charging. The PCEF enforces the policies delivered or specified by the PCRF. Specifically, the PCEF detects and measures the service data flows, ensures the QoS of the service data flows, processes the user-plane traffic, and triggers the control-plane session management. The PCEF may exist in a network entity such as a PDN GW in a System Architecture Evolution (SAE) network.
BBERF (included in an S-GW): The BBERF is capable of bearer binding, uplink bearer verification, and event reporting. The BBERF may exist in a network entity such as an S-GW in the SAE network, or a non-3GPP access gateway in a non-3GPP network.
FIG. 2 shows a multi-PDN scenario. In this scenario:
1. A User Equipment (UE) is connected to different external PDNs (PDN1 or PDN2 in FIG. 2);
2. The UE is connected to the PDN through an S-GW or a non-3GPP access gateway, and one or more P-GWs;
3. The PDN-GW creates an IP-CAN session (Gx1 and Gx2 in FIG. 2) for every external PDN connection of the UE;
4. If the S-GW or the non-3GPP access gateway communicates with the PDN-GW through PMIP, the S-GW creates a gateway control session (Gxx1 and Gxx2 in FIG. 2) for every external PDN connection of the UE; and
5. If the non-3GPP access gateway communicates with the PDN-GW through the Client Mobile Internet Protocol (CMIP), the S-GW creates a gateway control session (not illustrated in FIG. 2) for the UE.
In this scenario, the S9 session is created for every UE. The S9 interface has only one session. The gateway control session and all information of the IP-CAN session are sent as S9 session information. The first IP-CAN session or gateway control session triggers creation of the S9 session, and creation, modification or deletion of every subsequent IP-CAN session or gateway control session triggers modification or deletion of the S9 session.
As regards the multi-PDN scenario, the inventor finds at least the following problems in the prior art in the process of implementing the present disclosure:
The S9 session is unable to distinguish or handle creation, modification or deletion of the IP-CAN session and the gateway control session, and thus the V-PCRF is unable to understand the information delivered by the H-PCRF and unable to send the information to the correct PCEF or BBERF for enforcement, which leads to failure of the PCC function; if the V-PCRF is unable to report the PDN connection release information to the H-PCRF, the H-PCRF is unable to release the corresponding PDN connection, which leads to ineffective occupation of resources and incorrect policies.